As I was voting on images, I accidentally pressed the "down" button instead of the "up" button on an image. I then noticed that I cannot change the vote. So, I had an idea.

I'm not sure how the voting mechanic works, but could you make it so that, if one of the voting buttons are pressed, that button will be worth 0 and the other is worth 2 (or -2, for down) points on future presses by that user.

This would have to be updated every time that a score is changed, so that a person can't vote "up" once, then spam "down" votes (or vice-versa).

Additional Info:

Dolljoints replied at 2010-11-28 16:56:47

This is pretty much a duplicate of #187.

One thing to consider is privacy impact. If you store the fact that a user or IP voted, but not which way they voted, then their voting record cannot be held against them.